Methods and arrangements for controlling the speed of vehicles are known from the state of the art in many variations. For example, SAE Paper No. 961010 entitled "Adaptive Cruise Control, System Aspects and Development Trends" (1996) discloses a road speed controller while considering the spacing to the vehicle ahead. The driver inputs the desired speed of the vehicle via an operator adjustable lever with the functions which are customary for road speed controllers, such as setting a speed, resume speed, accelerate, et cetera. The desired speed is controlled in a manner comparable to a conventional vehicle road speed controller when a forward vehicle is not present in that a desired acceleration a.sub.FGR is computed from the difference between the desired and driving speeds. If a radar system detects a forward vehicle, then the spacing and the relative speed to this vehicle are determined. The control task in this case is that the relative speed is controlled to zero and simultaneously a desired spacing is maintained which is dependent upon speed. Parameters for determining the desired spacing (time gap) are adjustable by the driver. This follower controller determines a desired acceleration a.sub.fol from the above-mentioned variables. The desired acceleration a.sub.fol is, however, limited by the acceleration a.sub.FGR so that the pregiven desired speed cannot be exceeded even in the follower control. Distance controllers and speed controllers provide desired values for the acceleration and deceleration, respectively, of the vehicle in dependence upon the operating state. These desired values can be adjusted by influencing the engine of the vehicle and/or the brakes.
German patent publication 4,338,399 discloses a road speed controller wherein a desired acceleration of the vehicle is pregiven on the basis of the difference between the desired and actual speeds. This desired acceleration is adjusted by controlling the engine and/or by actuating the wheel brakes of the vehicle.
U.S. Pat. No. 4,337,511 discloses a road speed controller wherein the vehicle speed is adjusted only by influencing the engine power. A time-dependent change of the desired speed is provided in dynamic operating states, namely, during acceleration, deceleration and resume speed. This desired speed guides the vehicle with a pregiven acceleration or deceleration to the desired or stored desired value.
In all of these road speed controls, an operating state can occur wherein the road speed controller is switched off for time intervals and the vehicle moves at a significantly higher speed than the speed which is stored in the previous control operation.
This operating state can, for example, occur when the driver actuates the accelerator pedal to accelerate and increases the speed of the vehicle considerably above the stored desired speed.
In such operating situations, a reduction in comfort can occur with the actuation of the resume-speed key of the road speed controller because the road speed controller greatly decelerates the vehicle to reach the stored speed which is lower than the actual speed.